Add automake 1.13+ test outputs to .gitignore
app,libgimp,pdb: add a "drawable_color" PDB group

Which contains all the API from the "color" group, but with a
gimp_drawable namespace and with support for high bit depths. The
group is actually a copy of "color" with cruft removed and some API
ported to using float instead of integer API.

Deprecated all "color" functions that already have a ported version in
"drawable_color".

This is unfinished WIP, some functions in "drawable_color" still have
the old API.
libgimp: fix typo in gimp.def
pdb: add translation context to the newly added PDB functions
po: add drawable-color-cmds.c to POTFILES.in
build/win: Upgrade gdk-pixbuf2 to 2.30.2
build/win: Upgrade poppler to 0.24.5
build/win: Upgrade freetype2 to 2.5.2
build/win: Upgrade libpng to 1.6.8
build/win: Upgrade gdk-pixbuf2 to 2.30.3